Spinel powder and spinel slurry

Abstract

The invention features an MgAl2O4 spinel powder having a specific surface area of 40 m2/g or more and an average diameter of from 3 to 20 mum and having uniform pores, and a slurry containing this spinel powder. The spinel powder is produced by milling (1) an MgAl2O4 spinel powder obtained by synthesizing by the coprecipitation method with the use of hydroxide materials wherein the ratio of the average diameter of aluminum hydroxide "D1" to the average diameter of magnesium hydroxide "D2" satisfies the requirement 1.85<=(D1/D2) or 0.5>(D1/D2) and calcining, (2) an MgAl2O4 spinel powder obtained by drying a mixture solution containing water-soluble organic substance having a boiling point of 120° C. or above, converting the dried substance into a complex oxide by heating, or (3) a powder comprising as the main component an MgAl2O4 spinel powder which is obtained by mechanically mixing and milling a mixture of hydroxides for producing a spinel powder to convert into a complex hydroxide, and then heating a mixture composition containing the obtained complex hydroxide with an unconverted hydroxide to thereby convert into a complex oxide.

What is claimed is:  
     
       1. A spinel powder represented by a chemical formula MgAl 2 O 4 , wherein 
       the spinel powder has a specific surface area of 40 m 2 /g or more;  
       an average diameter of the spinel powder ranges from 3 to 20 μm; and  
       pores in the spinel powder having diameters falling within a range of d±d/2 from a mean pore diameter d, where 11 nm≦d<50 nm, form at least 70% of the total pore volume of the spinel powder.  
     
     
       2. The spinel powder as claimed in claim  1 , wherein the specific surface area of the spinel powder is 80 m 2 /g or more. 
     
     
       3. The spinel powder as claimed in claim  1 , wherein the spinel powder is produced by a process comprising 
       preparing a hydroxide, and  
       calcining the hydroxide.  
     
     
       4. The spinel powder as claimed in claim  3 , wherein the preparing comprises coprecipitation of aluminum hydroxide and magnesium hydroxide. 
     
     
       5. The spinel powder as claimed in claim  1 , wherein the spinel powder is produced by a process comprising 
       preparing an aluminum salt by dissolving aluminum hydroxide in an acid,  
       preparing a magnesium salt by dissolving magnesium hydroxide in an acid,  
       reacting the aluminum salt and the magnesium salt to form a reacted product, and  
       calcining the reacted product.  
     
     
       6. The spinel powder as claimed in claim  5 , wherein a ratio D 1 /D 2  of an average diameter of the aluminum hydroxide D 1  to an average diameter of the magnesium hydroxide D 2  is in a range of 1.85≦(D 1 /D 2 ) or 0.5>(D 1 /D 2 ). 
     
     
       7. The spinel powder as claimed in claim  1 , being in the form of a spinel slurry. 
     
     
       8. A method of making a spinel powder, the method comprising 
       mixing aluminum hydroxide and magnesium hydroxide, and  
       forming the spinel powder of claim  1 .  
     
     
       9. A spinel powder represented by a chemical formula MgAl 2 O 4 , wherein the spinel powder has a specific surface area of 55 m 2 /q or more and an average diameter of from 3 to 20 μm; and 
       pores in the spinel powder having diameters falling within a range of d±d/2 from a mean pore diameter d, where 11 nm≦d<50 nm, form at least 70% of the total pore volume of the spinel powder; and  
       the spinel powder is produced by a process comprising  
       drying a solution containing a water-soluble organic substance having a boiling point of 120° C. or above to form a dried substance, and  
       converting the dried substance into a complex oxide by heating and then milling.  
     
     
       10. The spinel powder as claimed in claim  9 , wherein the spinel powder is substantially free from a crystalline phase other than a MgAl 2 O 4  spinel phase. 
     
     
       11. The spindle powder as claimed in claim  9 , wherein the solution comprises water, a water-soluble inorganic aluminum salt and a water-soluble inorganic magnesium salt. 
     
     
       12. The spinel powder as claimed in claim  9 , wherein the water-soluble organic substance is at least one member selected from the group consisting of monohydric alcohols, polyhydric alcohol monomers, dimers, trimers and oligomers each having a boiling point of 120° C. or above, water-soluble polymer compounds containing polymers of the polyhydric alcohols having a boiling point of 120° C. or above, monosaccharides, disaccharides, polysaccharides, carbohydrates, carboxylic acids, salts of carboxylic acids and surfactants. 
     
     
       13. The spinel powder as claimed in claim  9 , being in the form of a spinel slurry. 
     
     
       14. A spinel powder represented by a chemical formula MgAl 2 O 4 , wherein the spinel powder has a specific surface area of 55 m 2 /q or more and an average diameter of from 3 to 20 μm; and 
       pores in the spinel powder having diameters falling within a range of d ±d/2 from a mean pore diameter d, where 11 nm≦d<50 nm, form at least 70% of the total pore volume of the spinel powder; and  
       the spinel powder is produced by a process comprising  
       drying a solution containing an aluminum salt of a water-soluble carboxylic acid and a magnesium salt of a water-soluble carboxylic acid to form a dried substance, and  
       converting the dried substance into a complex oxide by heating.  
     
     
       15. The spinel powder as claimed in claim  14 , wherein the spinel powder is substantially free from a crystalline phase other than a MgAl 2 O 4  spinel phase. 
     
     
       16. The spinel powder as claimed in claim  14 , being in the form of a spinel slurry. 
     
     
       17. A spinel powder comprising MgAl 2 O 4  as a main component, 
       wherein the spinel powder has a specific surface area of 42 m 2 /q or more and an average diameter of from 3 to 20 μm; and  
       pores in the spinel powder having diameters falling within a range of d±d/2 from a mean pore diameter d, where 11 nm≦d<50 nm form at least 70% of the total pore volume of the spinel powder; and  
       the spinel powder is produced by a process comprising  
       mechanically mixing and milling a mixture of hydroxides to form a complex hydroxide,  
       mixing the complex hydroxide with an unconverted hydroxide to form a mixture, and  
       heating the mixture to form a complex oxide.  
     
     
       18. The spinel powder as claimed in claim  17 , wherein the complex hydroxide is a water-containing salt. 
     
     
       19. The spinel powder as claimed in claim  17 , wherein the mechanical mixing and milling are carried out in a medium-mixing mill. 
     
     
       20. The spinel powder as claimed in claim  17 , wherein the hydroxide comprises magnesium hydroxide and aluminum hydroxide. 
     
     
       21. The spinel powder as claimed in claim  17 , being in the form of a spinel slurry.